Impeller for centrifugal apparatus



March 25, 1947. 'r. CHESTER IMPELLER FOR CENTRIFUGAL APPARATUS 2Sheets-Sheet 1 Filed Sept. 20, 1945 T. CHESTER IMPELLER FOR QENTRIFUGALAPPARATUS Match 25, 1947.

Filed Sept. 20, 1943 2 Sheets-Sheet 2 Patented Mar. 25, 1947 UNITEDSTATES PATENT OFFICE 2,418,012 IMPELLER FOR CENTRIFUGAL APPARATUSThomasChester, Detroit, Mich. Application September 20, 1943, Serial No.503,134

11 Claims.

impeller, the fluid being discharged from a plurality of tangentialports at the periphery of the impeller into the volute of the casing andthence through an outlet opening from the casing.

Anobject of the present invention is to provide an improved impellerblade which accelerates the fluid entering the ports between the bladeswith a minimum of turbulence and loss of power.

Another object of the invention is to provide an improved impeller forcentrifugal apparatus in which the impeller is provided with a pluralityof hollow blades with concave frontal surfaces facing in the directionof impeller rotation and convex back surfaces having ports therebetweenwhich enable acceleration of the fluid from sub stantial rest withreference to arcuate motion around the axis of the impeller to highvelocity without substantial turbulence.

Another object of the invention is to provide an improved impeller forcentrifugal apparatus in which the forward surfaces of hollow blades areconcave and in which the rear surfaces of the blades adjacent theradially inner tips thereof make a relatively low angle with a linejoining the radially inner tips of adjacent blades.

A further object of the invention is to provide an improved impeller forfluid pumps or fans in which a plurality of axially-extending blades inthe form of portional crescents have concave forward surfaces facing inthe direction of impeller rotation and rear surfaces backwardly inclinedat an angle in consonance with theneutral path of the fluid which entersthe ports of a rotating impeller to provide acceleration of the fluidthrough the ports between said blades with minimum turbulence.

Other objects and advantages of the invention will appear in thefollowing description of preferred embodiments thereof made inconnection with the attached drawing in which Fig. 1 is a verticalsection through an impeller in accordance with the present inventiontaken on the line l-i of Fig. 2;

Fig. 2 is a side elevation of the device of Fig. 1

with parts broken away to show the shape and arrangement of the impellerblades; 7

Fig. 3 is a fragmentary detail view on an enlarged scale showing onetype of blade;

Fig. 4 is a view similar to Fig. 3 showing a modified type of blade; and

Fig. 5 is another view similar to Fig. 3 showing a still furthermodified type of blade.

Referring particularly to the drawings, the

impeller of the present invention may comprise.

any suitable type of supporting structure such as a backing ring securedto a hub ll rigidly mounted upon a shaft l2, which in turn is supportedin suitable bearings (not shown) and rotated from a source of power(also not shown). The impeller may also include a plurality of axiallyextending blades l4 secured to the backing plate I0 in any suitablemanner,. such as by welding, and the extending ends of the blades may besimilarly secured to a shroud ring I5. The

.impeller is also preferably provided with an rearward face adjacent theradially meta internal deflector It for directing the fluid radiallyoutward into the ports I! between the blades l4 to secure uniformnon-turbulent flow through the interior of the impeller. The deflectorI6 is preferably a parabola or approximate parabola in axial section.While such deflector measurably increases the emciency of the device,improved results over prior impellers may be obtained .even if thedeflector It be omitted.

A suitable blade in accordance with the present invention is shown byway of example in Fig. 3. The blades I4 of this figure are shown asbeing substantially crescent shaped with the points of the crescentforming the radially inner and outer tips l8 and I9, respectively, ofthe blades. In general, the forward face of the blades will be concavealthough the radially inner portion 'of the forward face may, in someinstances be substantially straight. It will be further observed thatthe portion 20 of the rearward face of the blades adjacent the radiallyinner tip makes a rather small angle with a line joining the radiallylnner tip of such blade and the corresponding tip of the next succeedingblade. In general, it has been found that this angle should not begreater than approximately 40 and that it may be as small as 10 or evensmaller depending upon the speed at which the impeller is rotated andupon the required relationship between static pressure and velocitypressure, the smaller angles. .f being employed with higher speedimpellers and when the static pressure has a high ratio to; velocitypressure. As shown, the portlonno ,the

preferably substantially straight although it may be slightly curved andin general the rearward surface of any one blade is'preferablyapproximately parallel to the forward face of the next succeeding blade.However, with full crescent shaped blades a port which first con vergesand thendiverges with respect to the direction of fluid'flow, as shownin Fig. 3, may be advantageously employed. With the structure shown,fluid entering the ports between the blades is uniform- 1y acceleratedwithout turbulence and delivered at high velocity from the periphery ofthe impeller.

The modified blades 22 shown in Fig. 4 are illustratively substantiallysimilar to the radially inner halves of the blades of Fig. 3 and, toillus-- trate this, the remaining halves of certain of the crescents aredotted at 23 in Fig. 4. The blade form shown in Fig. 4 may be consideredto be a portional crescent without limitation to half a crescentillustratively shown thereby and the angle which the portion 24 of therear surface of the blade adjacent the radially inner tip makes with aline joining the said radially inner tip with the corresponding tip ofthe next succeedin blade may be substantially that described withreference to Fig. 3. It will be noted that the forward face of theblades of Fig. 4 are rearwardly inclined and in general such rearwardinclination is desirable, although the forward faces may have otherinclinations as is .old in the art. Again, the forward faces arepreferably concave as shown in Fig. 4 but may be substantially straight.In the impeller of Fig. 4 fluid entering the ports between the blades isalso uniformly accelerated and discharged outwardly from the ports oftheimpeller with relatively high velocity and with minimum turbulence inthe impeller.

The blades of Fig. 5 are a still further modification of the blades ofFigs. 3 and 4 in that a portion of a crescent elongated in thecircumferential direction of the impeller periphery is employed.Substantially the same considerations as to the inclination of theforward faces of the blades and also rearward faces of the blades asdiscussed with reference=to Fig. 4 are also contemplated for the bladesof Fig: 5. Thus, the

portions 21 of the rear surfaces of each of the blades adjacent theradially inner tip thereof make a relatively small angle with a linejoining the radially inner tip of the blade and that of the nextsucceeding blade. It will be noted that the hollow blades have increasedarcuate width in relationltoradial depth as compared with theprecedinggflgures, although the arrangement shown is illustrative andthe circumferential spacing or pitcli'land also the radial depth can bedifferent fro accelerated in its flow through the ports between theblades and dischargedv from the impeller with minimum turbulence intheimpeller.

From the above description it will be apparent thatlthe blades of Figs.4 and 5 may be termed portionalijcre'scents derived from the fullcrescent blades crrig. 3 and that in all of the blade constructions.described, the radially inner portion of e s the .bladelmay beconsidered to be a portional crescent. While all of the bladesillustrated are" shown as having a hollow structure, it is apparent thatsolid blades may be employed, particularly for impellers having bladesof small size. From Figs. 4 and 5 it will also be apparent that theblades are substantially portional crescents injcross section, formed bythe truncation or omission of the radially outer portion of the ,lthatshown. Again the fluid is uniformly 4 blades shown by Fig. 3. Thistruncation is important because it eliminates the necessity of the fluidmoving forward along the removed blade portion, with an angular orrotational velocity in excess of the impeller peripheral speed andthereby prevents instability of performance.

One of the important factors providing the increased eflieiency of thepresent invention is the the spacing can be greater than that shown.

However, the port width measured at approximately half the radial depthof the full crescent, thatis, at the radially outer portion of thesubstantially triangular blades of Figures 4 and 5, is preferably notgreater than approximately half of the arcuate pitch or spacing of theblades, and this port width should not be less than approximately 35% orgreater than approximately 65% 'of the distance between correspondingpoints on adjacent blades measured on they circle at half the radialdepth of the full crescents. The ratio of blade radial depth to impellerdiameter shown as indicated in Fig. l is merely by way of example andthis ratio can be varied within wide limits. Also, the impeller can havea greater or lesser axial length than that shown in Fig. 1 for the samediameter. Preferably all of the corners or tips of the blades shown inFigs. 3,4 and 5 are somewhat rounded although these corners may berelatively sharp without material decrease in efliciency of the device.In Figs. 4 and 5 the portional crescent shaped blades'are approximatelytriangular in outline, the radially inner tip of each blade constitutingthe apex and the radially outer side constituting the base. i Whenconsidered desirable these outer sides can be omitted or eliminated, inorder to reduce centrifugal stresses or for other reasons.

While I have disclosed the preferred embodiments of my invention it isunderstood that the details thereof may be varied with considerableamplitude without departing from the spirit, and essence of theinvention.

I claim:

1. In a rotary impeller for imparting motion to a fluid, a plurality ofaxially extending blades circumferentially spaced adjacent the,periphery of said impeller; each of said blades being approximately inthe form of a portional crescent and positioned to have the point ofsaid portional crescent form the radially inner tip of said blade and toprovide a convex rearward surface with respect to the direction ofrotation of said impeller, the portion of said rearward surface adjacentsaid radially inner tip forming an angle with a line joining saidradially inner tip with the corresponding tip of the next succeedingblade which is between approximately 10 and 40.

2. In a rotary impeller for imparting motion to a fluid, a plurality ofaxially extending blades circumferentially spaced adjacent the peripheryof said impeller, each of said blades being substantially in the form ofapproximately a half crescent positioned to have the point of said halfand to provide a convex rearward surface with respect to the directionof rotation of said impeller, the portion of said rearward surfaceadjacent said radially inner tip forming an angle with a line joiningsaid radially inner tip with the corresponding tip of the nextsucceeding blade which is between approximately and 40.

3. In a rotary impeller for imparting motion to a fluid, a pluralityofaxially extending blades circumferentially spaced adjacent the peripheryof said impeller, each of said blades havingsubstantially the form of aportional crescent positioned to have the point of said portionalcrescent form the to provide a convex rearward surface with respect tothe direction of rotation of said impeller, said rearward surface beingrearwardly inclined, the forward surface of said blades being sopositioned that a line joining said radially inner tip and the radiallyouter extremity of said forward surface is rearwardly inclined and therearward surface of said blades being positioned with respect to saidforward surface to provide ,ports between said blades which havesubstantially uniform width throughout each port when measured normallyof said rearward surface.

4. In a rotary impeller for imparting motion to a fluid, a plurality ofaxially extending blades circumferentially spaced adjacent the peripheryeach of said blades being substantially convex with its radially innerportion inclined at an angle not greater than approximately 40 to a linejoining the radially inner tip of said blade to the IUD radially innertip of said blade and of said impeller, each of said blades beingsubstantially in the form of a portional crescent poresponding tip of.the next succeeding blade which is between approximately 10 and theforward surface of said blades being so positioned that a line joiningsaid radially inner tip and the radially outer extremity of said surfaceis approximately radial.

5. In a rotary impeller for imparting motion to a fluid, a plurality'ofhollow blades each having the form of a portional crescent truncated'bythe omission of the radially outer tip, said portional crescent beingelongated in the circumferential direction of the impeller periphery anddisposed about the circumference of, said impeller, the frontal face ofeach of said blades with reference to the direction of impeller rotationbeing approximately radial and the back face of each of said bladesbeing substantially convex with its radially inner portion inclined atan angle not greater than approximately 40 to a line joining theradially inner tip of said blade to the radially inner tip of the nextfollowing blade, the

' width of the port between successive blades measured at half theradial depth of the full crescent bein not greater than approximatelyhaif of the arcuate pitch of the blades.

6. In a rotary impeller for imparting motion to a fluid, a plurality ofhollow blades each having in cross section the shape of a truncatedcrescent and disposed about the circumference of said impeller, thefrontal face of each of said blades being concave and inclined withreference to the direction of impeller rotation in accordance with therequired relationship between total pressure and the peripheral velocityand the back face of said radially radially inner tip of the nextfollowing blade, the circumferential width of the port betweensuecessive blades measured at half the radial depth of the full crescentbeing not greater than approximately half of the arcuate pitch of thelades.

7. In a rotary impeller for imparting motion to a fluid, a plurality ofaxially extending blades circumferentially spaced adjacent the peripheryof said impeller, each of said blades being substantially in the form ofa portional crescent positioned to have the point of said portionalcrescent form the radially inner tip of said blade and to provide aconvex rearward surface with respect to the responding tip of the nextsucceeding blade which is between approximately 1,0" and 40, and

and rear surfaces of said blades being positioned to provide a porttherebetween which has substantially uniform width throughout said portwhen measured normally of the said rearward surface. i

8. In a rotary impeller for imparting motion to a fluid, a plurality ofaxially extending blades stantially triangular in cross section with onecorner directed inwardly to form a radially inner tip of said blade,each of said blades having a concave forward surface and a convexrearward surface with respect to the direction of rotation of saidimpeller, said forward and rearward surfaces being positioned to provideports between the blades having substantially uniform width throughoutsaid ports when measured normally of said rearward surface.

9. In a rotary impeller for imparting motion to a fluid, a plurality ofaxially extending blades circumferentially spaced adjacent the peripheryof said impeller, each of said blades having substantially the form of aportional crescent positioned to have the point of said portionalcrescent form the radially inner tip of said blade and to provide spectto the the portion a convex rearward surface with redirection ofrotation of said impeller, of said rearward surface adjacent inner tipforming an angle with a line joining said radially inner tip with thecorresponding tip of the next succeeding blade pitch of the blades.

10. In a rotary impeller for imparting motion to a fluid, a plurality ofaxially extending blades mferentially spaced adjacent the periphery ofsaid impeller, each of said blades having the shape of a fractionalcrescent and being positioned to have the point of said fractionalcrescent form the radially inner tip thereof and to provide a convexrearward surface with respect to. the direction of rotation of saidimpeller, said rearward surface being inclined backwardly and theforward and rearward surface of adjacent blades being positioned toprovide a port therebetween which has substantially uniform widththroughout'said port when measured normally of said rearward surface,the circumferential width of the port between successive blades measuredat half the radial depth of the full crescent being not greater thanapproximately half of the arcuate pitch of the blades.

11. In a rotary impeller for imparting motion to a fluid. a plurality ofaxially extending blades circumferentially spaced adjacent the peripheryof said impeller, each of said blades being substantially triangular incross section with one corner directed inwardly to form a radially innertip of said blade, each of said blades having a concave forward surfaceand a convex rearward surface with respect to the direction of rotationof said impeller, said forward and rearward surfaces being positioned toprovide ports between the blades having substantially uniform widththroughout said ports when measured normally of said rearward surface,the portion of said rearward surface adjacent said radially inner tipforming an angle with a line joining said -,radially inner tip withthecorresponding tip of the next succeeding blade which is betweenapproximately 10 and 40 degrees, said ports having a circumferentialwidth measured at the radially outer portion of said blades which is notgreater than approximately half of the arouate pitch of the blades.

THOMAS crmsrm.

aaraacncas crrap The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 10 Number Number French Aug. 12, 1878 Certificateof Correction Patent No. 2,418,012.

LESLIE FRAZER,

Fz'w'st Assistant Commissioner 0 f Patents.

